1. Field of the Invention
An aspect of the present invention relates to a rechargeable battery, and, more particularly, to a rechargeable battery having an improved casing structure.
2. Description of the Related Art
A rechargeable battery may be repeatedly charged and discharged while a primary battery is not rechargeable. A low capacity rechargeable battery may be used in portable miniaturized electronic devices, such as mobile phones, laptop computers, and camcorders. A large capacity battery, obtained by connecting a plurality of battery cells, may be widely used as a power supply to drive motors of movable electric apparatuses, such as hybrid electric vehicles (HEV).
The rechargeable battery (hereinafter, referred to as “a unit battery”) includes an electrode assembly including positive and negative electrodes and a separator interposed therebetween, a casing in which the electrode group is stored, and a cap assembly assembled with the casing to seal the casing, having an electrode terminal that is electrically connected to the electrode assembly.
The unit battery may be cylindrical or rectangular. In the rectangular unit battery, the electrode assembly is electrically connected to the electrode terminal through a lead member. In this case, the lead member is fixed to the electrode assembly using ultrasonic welding, and the lead member is fixed to the overlying electrode terminal. Such an interconnection structure between the electrode assembly and the electrode terminal may deteriorate when the unit battery is externally impacted and the electrode assembly shakes due to the impact so that a welded portion between the electrode assembly and the lead member is damaged or broken.
When the electrode assembly is broken off from the lead member or attached to the lead member in a damaged condition, as described above, a sufficient amount of the current extracted to the electrode assembly may not flow out of the unit battery via the electrode terminal. As a result, the unit battery may not function as a power supply.
Furthermore, electrical resistance may inevitably increase in a contact area of the deteriorated interconnection between the electrode assembly and the lead member. As a result, an electrical charge/discharge efficiency of the unit battery may be degraded, and heat may be generated in the contact area that causes an increase in an internal temperature of the unit battery. As a result, the unit battery may malfunction.
Moreover, if the electrode assembly is not robustly supported in the casing, the electrode assembly may lean when the unit battery is continuously vibrated depending on an installation environment thereof. As a result, the aforementioned interconnection structure between the electrode assembly and the electrode terminal may degrade the charge/discharge efficiency as electrolyte contained in the casing cannot appropriately react.